PSM Application Note r2
Table Of Contents
- Notice
- Copyrights
- Computer Software Copyrights
- Usage and Disclosure Restrictions
- APPLICABILITY TABLE
- CONTENTS
- 1. Introduction
- 2. OVERVIEW
- 3. PSM DESCRIPTION
- 4. PINS ALLOCATION
- 5. Glossary and Acronyms
- 6. Document History
80471NT11483A Rev. 2 Page 20 of 24 2017-06-06
Enter and Exit from PSM States
Since the LE866 outputs become inputs\non-defined during the PSM states, the module
and the host should follow a specific protocol to ensure the proper system operation:
• LE866 notifies the host before going into a PSM state by setting PSM_STATUS low
• Host makes proper preparations and notifies the LE866 he is allowed to enter the
PSM state by setting the PSM_WAKE low (this could be avoided if a pull down
resistor is added to the PSM_WAKE line)
• LE866 enters in PSM state
• If required, the host can wake the LE866 at any time by setting the PSM_WAKE line
high.
• LE866 notifies the host when it is out of the PSM states by setting PSM_STATUS
high
• Host keeps the PSM_WAKE line high to ensure the module does not enter the PSM
states without proper coordination and permission from the host.
If required on specific applications or by specific hosts, it is possible to add dedicated
external logic to toggle the PSM_WAKE pin high, when there is an event on the preferred
pin/interface (for example on the UART RTS)
The following diagram shows the process of PSM enter/exit due to Host request: